Foodstuff wrapping having a rough and naturally appearing surface

ABSTRACT

A description is given of a single-layer or multilayer food casing made of a thermoplastic mixture which comprises at least one aliphatic polyamide and/or copolyamide, at least one inorganic and/or organic filler and if appropriate at least one aliphatic and/or partially aromatic copolyamide having glycol units and/or polyglycol units. The casing has a maximum surface roughness R max , determined in accordance with DIN 4768, of 3 to 60 μm, and a water vapor permeability at a mean thickness of 100 μm, determined as specified in DIN 53122, of less than 50 g/m 2 .d. It thus has a particularly matte, rough, and very natural surface structure. The casing is produced by extrusion using an annular die and subsequent film blowing or biaxial stretch orientation. It is suitable as an artificial sausage casing, especially for scalded-emulsion sausage.

The present invention relates to a single-layer or multilayer foodcasing made of a thermoplastic mixture which comprises at least onealiphatic polyamide and/or copolyamide, and also its use as artificialsausage casing, in particular for smoked scalded-emulsion sausage.

Food casings, especially sausage casings, are produced from natural gutskin, textile skin, fiber skin or cellulose skin, collagen or plastic.Although the collagen or hide-fiber skin is distinguished by a naturalsurface and a pleasant feel quality, it is produced by a very complexand environmentally polluting process from cattle hides. The hide tissueis digested with acids (for example lactic acid) down to the fibrils;the high-viscosity mass is extruded and slowly and in compact formprecipitated and solidified with gaseous ammonia or ammonium hydroxide.During drying, crosslinking (curing) then takes place to give theproducts sufficient stability, so that they withstand the scaldingprocess without significant loss of strength. Natural gut skins, andalso hide-fiber skins, however, are increasingly gaining less acceptancefrom the final consumers because of various incidents, such as the BSEinfection in cattle and the misuse of antibiotics. Furthermore, legalrestrictions are threatened. An alternative to said skins is thereforedesirable. Cellulose skins, even those with fiber reinforcement, canonly take over this task with restrictions. Their production process isalso no less complex and environmentally polluting than the collagenprocess.

Furthermore, cellulose casings and collagen casings not only have highsmoke permeability, but also high water vapor permeability. Thepermeability is generally more than 500 g/m²d. These high values arerequired for the ripening behavior in uncooked-meat sausageapplications, such as salami. However, in the case of smokedscalded-emulsion sausage varieties, they cause excessive drying of thesausage in the scalding process (risk of dry rim formation).Furthermore, unattractive leakage of juice from the sausage occurs inthe outer packaging.

Food casings based on synthetic polymers, in contrast, can be a truealternative. These can be produced very simply and without hygiene risksvia a combined extrusion and film-blowing process (if appropriatebiaxial stretching). However, pure plastic casings, owing to theirunnatural, smooth and glossy surface, have not been able to gainacceptance in the market sector for collagen skin or natural gut skin.In addition, they can only store a small amount of water and exhibitonly a low permeability for water vapor and smoke.

Plastic casings modified with natural substances are also known. ThusEP-B 0 711 324 describes a reinforced biodegradable non-foamed polymerwhich contains thermoplastic starch, a hydrophobic biodegradable polymerand a natural fiber such as ramie or sisal. It is used as an engineeringplastic for producing shaped bodies. EP-A 0 596 437 describes mixturesof starch or thermoplastic starch with, for example, aliphaticpolyesters or poly(vinyl alcohol) which may be processed bythermoplastic extrusion to form water-resistant biodegradable films.

EP-B 0 539 544 discloses a polymer mixture of starch, a plasticizer anda polyolefin. A material made of one or more synthetic polymers, forexample a homopolymer or copolymer of hydroxycarboxylic acids,polyurethanes, polyamides and vinyl alcohol copolymers and starch isdescribed in WO 92/19680.

In most uses of this type the biodegradability takes the leading role.Natural appearance and pleasant feel qualities are of secondaryimportance; the water vapor permeability plays a likewise minor role.

A smoke-permeable food casing is described in EP-A 920 808. As essentialconstituent it comprises cellulose acetate propionate, if appropriatemixed with an aliphatic polyamide or copolyamide, such as nylon 6, nylon6/6, nylon 12 or nylon 6/12. It can further comprise plasticizers, suchas phthalic acid esters, glycol derivatives or glycerol derivatives.

WO 99/61524 discloses food casings made of a thermoplastic mixturehaving a polysaccharide component and a plasticizer. They consist ofthermoplastic starch or thermoplastic starch derivative and athermoplastic polyester urethane (TPU). Seamless tubular casings made ofthis material have small sigma 15 values of about 3 to 4.5; that is tosay they are readily deformable and therefore do not exhibit sufficientcaliber constancy. The casings have a milky, matte optical appearance.However, they lack the roughness and slightly inhomogeneous structurewhich make up the natural feel quality of a collagen skin or natural gutskin. In addition, it is disadvantageous that these casings exhibit anundesirably high turbidity, as soon as they are surrounded by an outerpackaging of plastic film and as a result are exposed to highatmospheric humidity.

EP-B 0 935 423 discloses a polyamide-based sausage casing which containsblock copolymers having hard aliphatic polyamide blocks and softaliphatic polyether blocks. The water vapor permeability of such casingsis about 75 g/m²d. It is thus suitable in principle for smokedscalded-emulsion sausage varieties. However, its very glossy, smooth andartificial-seeming surface is criticized by the end users.

The two last-mentioned plastic casings have not been able to establishthemselves as an alternative to a traditional collagen skin or naturalgut skin, the former, especially, owing to their deficient caliberstability and their turbidity in the outer packaging, the latter becauseof their glossy, unnatural appearance.

The object was therefore to provide a food casing which is hygienicallysafe, simple to produce and which exhibits a particularly matte, roughand natural surface structure. Furthermore, the water vapor permeability(WVP) should be settable in a defined manner, being less than 50 g/m²d.The weight loss with smoked scalded-emulsion sausage varieties is to besmall, the tendency to form a dry rim minimal and the loss of juice inthe outer packaging is to be negligible. In addition it is to becoilable, able to be cut into hot and it is to be peelable withoutdefect from the food (generally a sausage-meat emulsion).

The object is achieved by incorporating an inorganic and/or organicfiller. The filler gives the casing a very natural silky-matteappearance and feel quality. The surface receives a slight roughness,which can be set via the type of filler. In addition, via the fillerproportion, the ability of the casing to coil can be influenced. Inaddition, the filler acts as a reinforcing agent, as a result of whichthe caliber stability of the filled material is markedly increasedcompared with the unfilled material. Finally, the fillers, in particularorganic fillers, cause increased smoke permeability, which likewise maybe set by type and proportion. Some fillers, furthermore, improve thewater storage capacity of the casing.

The present invention therefore relates to a single-layer or multilayerfood casing made of a thermoplastic mixture having at least onealiphatic polyamide and/or copolyamide and wherein the mixture comprisesat least one inorganic and/or organic filler, the casing having amaximum surface roughness R_(max), determined in accordance with DIN4768, of 3 to 60 μm, and a water vapor permeability at a mean thicknessof 100 μm, determined as specified in DIN 53122, of less than 50 g/m²d.Preferably, it has a water vapor permeability of 1 to 49 g/m²d. It isthus especially suitable for scalded-emulsion sausage varieties.

In the case of the multilayer casing, the thermoplastic mixture issituated in the outside layer.

Preferred polyamides and/or copolyamides (abbreviated: (co)polyamides)are nylon 6 (poly(ε-caprolactam)=polyamide of ε-caprolactam, or6-aminohexanoic acid), nylon 6.6 (poly(hexamethyleneadipamide)=polyamide of hexamethylene diamide and adipic acid), nylon6/6.6 (copolyamide of ε-caprolactam, hexamethylenediamine and adipicacid), nylon 6/66.9 (copolyamide of ε-caprolactam, hexamethylenediamine,adipic acid and azelaic acid), nylon 6/66.12 (copolyamide ofε-caprolactam, hexamethylenediamine, adipic acid and laurolactam), nylon6.9 (polyamide of hexamethylenediamine and azelaic acid), nylon 6.10(poly(hexamethylenesebacamide=polyamide of hexamethylene-diamine andsebacic acid), nylon 6.12 (poly(hexamethylene dodecanamide)=copolyamideof ε-caprolactam and ω-aminolaurolactam), nylon 4.6 (poly(tetramethyleneadipamide)=polyamide of tetramethylenediamine and adipic acid) or nylon12 (poly(ε-laurolactam)). The (co)polyamide causes especially a higherstiffness of the film.

If appropriate, the thermoplastic mixture additionally further containsat least one aliphatic and/or partially aromatic copolyamide havingglycol units and/or polyglycol units (abbreviated: polyether blockamide). The polyether block amide is preferably a block copolymer. Thepolyglycol blocks here generally have 5 to 20 glycol units, preferablyabout 7 to 15, particularly preferably about 10 glycol units. The termglycol is to be taken to mean here at least dihydric, aliphatic orcycloaliphatic alcohols having 2 to 15 carbon atoms. The terminalhydroxyl groups of the polyglycol blocks can be replaced by aminogroups. Such block copolymers are obtainable, for example, under thename ®Jeffamine.

The polyglycol part of the aliphatic or partially aromatic copolyamidecan also have ester segments. These consist of units of at least onebifunctional aliphatic alcohol, preferably ethylene glycol or1,2-propylene glycol (=propane-1,2-diol), and units of at least onedibasic aliphatic, cycloaliphatic or aromatic dicarboxylic acid,preferably adipic acid, sebacic acid or isophthalic acid.

The glycol- or polyglycol-modified copolyamide therefore comprises in apreferred embodiment

-   -   a) at least one amide part having units        -   a1) of at least bifunctional aliphatic and/or cycloaliphatic            amines (especially hexamethylenediamine or            isophoronediamine) and of at least bifunctional aliphatic            and/or cycloaliphatic and/or aromatic carboxylic acids            (especially adipic acid, sebacic acid,            cyclohexane-dicarboxylic acid, isophthalic acid or            trimellitic acid), or        -   a2) of aliphatic aminocarboxylic acids, in particular            o)-aminocarboxylic acids, or lactams thereof (especially            ε-caprolactam or ω-laurolactam) or        -   a3) mixtures of a1) and a2) and    -   b) at least one glycol or polyglycol part containing units        -   b1) of an at least bifunctional aliphatic and/or            cycloaliphatic alcohol having 2 to 15 carbon atoms, in            particular 2 to 6 carbon atoms (especially ethylene glycol,            propane-1,2-diol, propane-1,3-diol, butane-1,4-diol or            trimethylolpropane), or        -   b2) of at least one oligoglycol or polyglycol of one of the            alcohols specified in b1) (especially diethylene glycol,            triethylene glycol, polyethylene glycol or            poly(1,2-propylene glycol)) or        -   b3) of at least one aliphatic oligoglycol or polyglycol of            the type specified in b2), the terminal hydroxyl groups of            which are replaced by amino groups (Jeffamine) or        -   b4) of a mixture of b1), b2) and/or b3) or        -   b5) of an ester-containing polyglycol part formed from at            least bifunctional aliphatic alcohols (especially ethylene            glycol or 1,2-propylene glycol) and at least divalent            aliphatic, cycloaliphatic and/or aromatic dicarboxylic acids            (especially adipic acid, sebacic acid or isophthalic acid)            or        -   b6) of a mixture of b1), b2) and/or b5).

Preferably, the modified polyamide contains, in addition to saidconstituents, no others.

In a preferred embodiment, the thermoplastic mixture consists of atleast one (co)polyamide and at least one organic and/or inorganicfiller. The amount of (co)polyamide in this case is 50 to 99% by weight,preferably 60 to 98% by weight, particularly preferably 65 to 98% byweight, and the total amount of inorganic and/or organic filler is 1 to50% by weight, preferably 1 to 40% by weight, particularly preferably 2to 35% by weight, in each case based on the total weight of thethermoplastic mixture.

In another preferred embodiment, the thermoplastic mixture consists ofat least one (co)polyamide and at least one polyether block amide and atleast one organic and/or inorganic filler. In this case the amount of(co)polyamide is 35 to 98% by weight, preferably 45 to 97% by weight,particularly preferably 55 to 97% by weight, and the amount of polyetherblock amide is 1 to 35% by weight, preferably 2 to 30% by weight,particularly preferably 3 to 25% by weight, and the total amount ofinorganic and/or organic filler is 1 to 50% by weight, preferably 1 to40% by weight, particularly preferably 2 to 35% by weight, in each casebased on the total weight of the thermoplastic mixture.

The organic filler is, in particular, a carbohydrate. In this case it ispreferably a natural polysaccharide and/or a derivative thereof.Branched and crosslinked polysaccharides and derivatives thereof arelikewise suitable. Proteins can only be used with restrictions, since,under the high processing temperatures, they are to a large partdecomposed.

Particularly suitable polysaccharides are, for example, plant powders,fibers, fibrids or pulp from cellulose. They should have particle sizesor fiber lengths of 5 to 3000 μm, preferably 10 to 1000 μm, particularlypreferably 15 to 500 μm. These include plant hairs or seed fibers suchas cotton wool, kapok or akon, bast fibers such as flax or linen, hemp,jute, sunn, kenaf, urena, rosella or ramie, hard fibers such as sisal,henequen, manila, fique, phormium, esparto grass, turf, straw or yucca,fruit fibers such as coconut, pineapple, apple or orange, softwood andhardwood fibers such as spruce, pine or cork meal, other plant fibers,for example Tillandsia, and also fibers from wheat, potatoes, tomatoesor carrots.

It is also possible to use native starch, for example from potatoes,manioc, maranta (=arrowroot), sweet potato, wheat, corn, rye, rice,barley, millet, oats, sorghum, chestnuts, acorns, beans, peas, bananas,palm pith (sago). Corn starch is particularly preferred. The ratio ofamylose to amylopectin in the various starches can vary. The molecularweight M_(w) is expediently about 50 000 to 10 000 000.

Starch derivatives are, for example, grafted native starches. Graftingagents are, in particular, maleic anhydride, succinic anhydride or Foodcasing having a rough and natural-seeming surface.

The present invention relates to a single-layer or multilayer foodcasing made of a thermoplastic mixture which comprises at least onealiphatic polyamide and/or copolyamide, and also its use as artificialsausage casing, in particular for smoked scalded-emulsion sausage.

Food casings, especially sausage casings, are produced from natural gutskin, textile skin, fiber skin or cellulose skin, collagen or plastic.Although the collagen or hide-fiber skin is distinguished by a naturalsurface and a pleasant feel quality, it is produced by a very complexand environmentally polluting process from cattle hides. The hide tissueis digested with acids (for example lactic acid) down to the fibrils;the high-viscosity mass is extruded and slowly and in compact formprecipitated and solidified with gaseous ammonia or ammonium hydroxide.During drying, crosslinking (curing) then takes place to give theproducts sufficient stability, so that they withstand the scaldingprocess without significant loss of strength. Natural gut skins, andalso hide-fiber skins, however, are increasingly gaining less acceptancefrom the final consumers because of various incidents, such as the BSEinfection in cattle and the misuse of antibiotics. Furthermore, legalrestrictions are threatened. An alternative to said skins is thereforedesirable. Cellulose skins, even those with fiber reinforcement, canonly take over this task with restrictions. Their production process isalso no less complex and environmentally polluting than the collagenprocess.

Furthermore, cellulose casings and collagen casings not only have highsmoke permeability, but also high water vapor permeability. Thepermeability is generally more than 500 g/m²d. These high values arerequired for the ripening behavior in uncooked-meat sausageapplications, such as salami. However, in the case of smokedscalded-emulsion sausage varieties, they cause excessive drying of thesausage in the scalding process (risk of dry rim formation).Furthermore, unattractive leakage of juice from the sausage occurs inthe outer packaging.

Food casings based on synthetic polymers, in contrast, can be a truealternative. These can be produced very simply and without hygiene risksvia a combined extrusion and film-blowing process (if appropriatebiaxial stretching). However, pure plastic casings, owing to theirunnatural, smooth and glossy surface, have not been able to gainacceptance in the market sector for collagen skin or natural gut skin.In addition, they can only store a small amount of water and exhibitonly a low permeability for water vapor and smoke.

Plastic casings modified with natural substances are also known. ThusEP-B 0 711 324 describes a reinforced biodegradable non-foamed polymerwhich contains thermoplastic starch, a hydrophobic biodegradable polymerand a natural fiber such as ramie or sisal. It is used as an engineeringplastic for producing shaped bodies. EP-A 0 596 437 describes mixturesof starch or thermoplastic starch with, for example, aliphaticpolyesters or poly(vinyl alcohol) which may be processed bythermoplastic extrusion to form water-resistant biodegradable films.

EP-B 0 539 544 discloses a polymer mixture of starch, a plasticizer anda polyolefin. A material made of one or more synthetic polymers, forexample a homopolymer or copolymer of hydroxycarboxylic acids,polyurethanes, polyamides and vinyl alcohol copolymers and starch isdescribed in WO 92/19680.

In most uses of this type the biodegradability takes the leading role.Natural appearance and pleasant feel qualities are of secondaryimportance; the water vapor permeability plays a likewise minor role.

A smoke-permeable food casing is described in EP-A 920 808. As essentialconstituent it comprises cellulose acetate propionate, if appropriatemixed with an aliphatic polyamide or copolyamide, such as nylon 6, nylon6/6, nylon 12 or nylon 6/12. It can further comprise plasticizers, suchas phthalic acid esters, glycol derivatives or glycerol derivatives.

WO 99/61524 discloses food casings made of a thermoplastic mixturehaving a polysaccharide component and a plasticizer. They consist ofthermoplastic starch or thermoplastic starch derivative and athermoplastic polyester urethane (TPU). Seamless tubular casings made ofthis material have small sigma 15 values of about 3 to 4.5; that is tosay they are readily deformable and therefore do not exhibit sufficientcaliber constancy. The casings have a milky, matte optical appearance.However, they lack the roughness and slightly inhomogeneous structurewhich make up the natural feel quality of a collagen skin or natural gutskin. In addition, it is disadvantageous that these casings exhibit anundesirably high turbidity, as soon as they are surrounded by an outerpackaging of plastic film and as a result are exposed to highatmospheric humidity.

EP-B 0 935 423 discloses a polyamide-based sausage casing which containsblock copolymers having hard aliphatic polyamide blocks and softaliphatic polyether blocks. The water vapor permeability of such casingsis about 75 g/m²d. It is thus suitable in principle for smokedscalded-emulsion sausage varieties. However, its very glossy, smooth andartificial-seeming surface is criticized by the end users.

The two last-mentioned plastic casings have not been able to establishthemselves as an alternative to a traditional collagen skin or naturalgut skin, the former, especially, owing to their deficient caliberstability and their turbidity in the outer packaging, the latter becauseof their glossy, unnatural appearance.

The object was therefore to provide a food casing which is hygienicallysafe, simple to produce and which exhibits a particularly matte, roughand natural surface structure. Furthermore, the water vapor permeability(WVP) should be settable in a defined manner, being less than 50 g/m²d.The weight loss with smoked scalded-emulsion sausage varieties is to besmall, the tendency to form a dry rim minimal and the loss of juice inthe outer packaging is to be negligible. In addition it is to becoilable, able to be cut into hot and it is to be peelable withoutdefect from the food (generally a sausage-meat emulsion).

The object is achieved by incorporating an inorganic and/or organicfiller. The filler gives the casing a very natural silky-matteappearance and feel quality. The surface receives a slight roughness,which can be set via the type of filler. In addition, via the fillerproportion, the ability of the casing to coil can be influenced. Inaddition, the filler acts as a reinforcing agent, as a result of whichthe caliber stability of the filled material is markedly increasedcompared with the unfilled material. Finally, the fillers, in particularorganic fillers, cause increased smoke permeability, which likewise maybe set by type and proportion. Some fillers, furthermore, improve thewater storage capacity of the casing.

The present invention therefore relates to a single-layer or multilayerfood casing made of a thermoplastic mixture having at least onealiphatic polyamide and/or copolyamide and wherein the mixture comprisesat least one inorganic and/or organic filler, the casing having amaximum surface roughness R_(max), determined in accordance with DIN4768, of 3 to 60 μm, and a water vapor permeability at a mean thicknessof 100 μm, determined as specified in DIN 53122, of less than 50 g/m²d.Preferably, it has a water vapor permeability of 1 to 49 g/m²d. It isthus especially suitable for scalded-emulsion sausage varieties.

In the case of the multilayer casing, the thermoplastic mixture issituated in the outside layer.

Preferred polyamides and/or copolyamides (abbreviated: (co)polyamides)are nylon 6 (poly(ε-caprolactam)=polyamide of ε-caprolactam, or6-aminohexanoic acid), nylon 6.6 (poly(hexamethyleneadipamide)=polyamide of hexamethylene diamide and adipic acid), nylon6/6.6 (copolyamide of ε-caprolactam, hexamethylenediamine and adipicacid), nylon 6/66.9 (copolyamide of ε-caprolactam, hexamethylenediamine,adipic acid and azelaic acid), nylon 6/66.12 (copolyamide ofε-caprolactam, hexamethylenediamine, adipic acid and laurolactam), nylon6.9 (polyamide of hexamethylenediamine and azelaic acid), nylon 6.10(poly(hexamethylenesebacamide=polyamide of hexamethylene-diamine andsebacic acid), nylon 6.12 (poly(hexamethylene dodecanamide)=copolyamideof ε-caprolactam and ω-aminolaurolactam), nylon 4.6 (poly(tetramethyleneadipamide)=polyamide of tetramethylenediamine and adipic acid) or nylon12 (poly(ε-laurolactam)). The (co)polyamide causes especially a higherstiffness of the film.

If appropriate, the thermoplastic mixture additionally further containsat least one aliphatic and/or partially aromatic copolyamide havingglycol units and/or polyglycol units (abbreviated: polyether blockamide). The polyether block amide is preferably a block copolymer. Thepolyglycol blocks here generally have 5 to 20 glycol units, preferablyabout 7 to 15, particularly preferably about 10 glycol units. The termglycol is to be taken to mean here at least dihydric, aliphatic orcycloaliphatic alcohols having 2 to 15 carbon atoms. The terminalhydroxyl groups of the polyglycol blocks can be replaced by aminogroups. Such block copolymers are obtainable, for example, under thename ®Jeffamine.

The polyglycol part of the aliphatic or partially aromatic copolyamidecan also have ester segments. These consist of units of at least onebifunctional aliphatic alcohol, preferably ethylene glycol or1,2-propylene glycol (=propane-1,2-diol), and units of at least onedibasic aliphatic, cycloaliphatic or aromatic dicarboxylic acid,preferably adipic acid, sebacic acid or iso phthalic acid.

The glycol- or polyglycol-modified copolyamide therefore comprises in apreferred embodiment

-   -   a) at least one amide part having units        -   a1) of at least bifunctional aliphatic and/or cycloaliphatic            amines (especially hexamethylenediamine or            isophoronediamine) and of at least bifunctional aliphatic            and/or cycloaliphatic and/or aromatic carboxylic acids            (especially adipic acid, sebacic acid,            cyclohexanedicarboxylic acid, isophthalic acid or            trimellitic acid), or        -   a2) of aliphatic aminocarboxylic acids, in particular            co-aminocarboxylic acids, or lactams thereof (especially            ε-caprolactam or ω-laurolactam) or        -   a3) mixtures of a1) and a2) and    -   b) at least one glycol or polyglycol part containing units        -   b1) of an at least bifunctional aliphatic and/or            cycloaliphatic alcohol having 2 to 15 carbon atoms, in            particular 2 to 6 carbon atoms (especially ethylene glycol,            propane-1,2-diol, propane-1,3-diol, butane-1,4-diol or            trimethylolpropane), or        -   b2) of at least one oligoglycol or polyglycol of one of the            alcohols specified in b1) (especially diethylene glycol,            triethylene glycol, polyethylene glycol or            poly(1,2-propylene glycol)) or        -   b3) of at least one aliphatic oligoglycol or polyglycol of            the type specified in b2), the terminal hydroxyl groups of            which are replaced by amino groups (Jeffamine) or        -   b4) of a mixture of b1), b2) and/or b3) or        -   b5) of an ester-containing polyglycol part formed from at            least bifunctional aliphatic alcohols (especially ethylene            glycol or 1,2-propylene glycol) and at least divalent            aliphatic, cycloaliphatic and/or aromatic dicarboxylic acids            (especially adipic acid, sebacic acid or isophthalic acid)            or        -   b6) of a mixture of b1), b2) and/or b5).

Preferably, the modified polyamide contains, in addition to saidconstituents, no others.

In a preferred embodiment, the thermoplastic mixture consists of atleast one (co)polyamide and at least one organic and/or inorganicfiller. The amount of (co)polyamide in this case is 50 to 99% by weight,preferably 60 to 98% by weight, particularly preferably 65 to 98% byweight, and the total amount of inorganic and/or organic filler is 1 to50% by weight, preferably 1 to 40% by weight, particularly preferably 2to 35% by weight, in each case based on the total weight of thethermoplastic mixture.

In another preferred embodiment, the thermoplastic mixture consists ofat least one (co)polyamide and at least one polyether block amide and atleast one organic and/or inorganic filler. In this case the amount of(co)polyamide is 35 to 98% by weight, preferably 45 to 97% by weight,particularly preferably 55 to 97% by weight, and the amount of polyetherblock amide is 1 to 35% by weight, preferably 2 to 30% by weight,particularly preferably 3 to 25% by weight, and the total amount ofinorganic and/or organic filler is 1 to 50% by weight, preferably 1 to40% by weight, particularly preferably 2 to 35% by weight, in each casebased on the total weight of the thermoplastic mixture.

The organic filler is, in particular, a carbohydrate. In this case it ispreferably a natural polysaccharide and/or a derivative thereof.Branched and crosslinked polysaccharides and derivatives thereof arelikewise suitable. Proteins can only be used with restrictions, since,under the high processing temperatures, they are to a large partdecomposed.

Particularly suitable polysaccharides are, for example, plant powders,fibers, fibrids or pulp from cellulose. They should have particle sizesor fiber lengths of 5 to 3000 μm, preferably 10 to 1000 μm, particularlypreferably 15 to 500 μm. These include plant hairs or seed fibers suchas cotton wool, kapok or akon, bast fibers such as flax or linen, hemp,jute, sunn, kenaf, urena, rosella or ramie, hard fibers such as sisal,henequen, manila, fique, phormium, esparto grass, turf, straw or yucca,fruit fibers such as coconut, pineapple, apple or orange, softwood andhardwood fibers such as spruce, pine or cork meal, other plant fibers,for example Tillandsia, and also fibers from wheat, potatoes, tomatoesor carrots.

It is also possible to use native starch, for example from potatoes,manioc, maranta (=arrowroot), sweet potato, wheat, corn, rye, rice,barley, millet, oats, sorghum, chestnuts, acorns, beans, peas, bananas,palm pith (sago). Corn starch is particularly preferred. The ratio ofamylose to amylopectin in the various starches can vary. The molecularweight M_(w) is expediently about 50 000 to 10 000 000.

Starch derivatives are, for example, grafted native starches. Graftingagents are, in particular, maleic anhydride, succinic anhydride orε-caprolactone. Suitable starch derivatives are, in addition, starchesters, in particular starch xanthogenates, acetates, phosphates,sulfates, nitrates, maleates, propionates, butyrates, laurates andoleates. In addition, starch ethers, such as starch methyl ether, ethylether, propyl ether, butyl ether, alkenyl ether, hydroxyethyl ether,hydroxypropyl ether. Oxidized starches such as dialdehyde starch,carboxy starch or starch broken down with persulfate are likewisesuitable.

In addition, crosslinked carbohydrates can also be used. These arecrosslinked, for example, with urea derivatives, urotropin, trioxane,di- or polyepoxides, di- or polychlorohydrins, di- or polyisocyanates,carbonic acid derivatives, diesters or inorganic polyacids, such asphosphoric acid or boric acid.

Substances which are also suitable as filler are natural substances,such as olive stone flour, xanthan, gum arabic, gum gellan, gum ghatti,gum kraya, gum tragacanth, emulsan, rhamsan, wellan, schizophyllan,polygalacturonates, laminarin, amylose, amylopectin and also pectins. Itis also possible to use alginic acid, alginates, carrageenan,furcellaran, guar gum, agar agar, tamarind gum, aralia gum,arabinogalactan, pullulan, carob bean gum, chitosan, dextrins,1,4-α-D-polyglucan. The molecular weight M_(w) of said carbohydrates isgenerally from 500 to 100 000.

It is also possible to use synthetic fibers or powders (for examplepolyethylene, polypropylene, polyamide, polyacrylonitrile, polyesterfibers). Those which are particularly suitable are synthetichigh-temperature-stable fibers or powders based on fluoropolymers,polysulfones, polyether sulfones, polyether ketones, polyphenylenesulfides, polyaramids, polyimides, aromatic polyesters,polyquinoxalines, polyquinolines, polybenzimidazoles, liquid-crystalpolymers and conducting polymers, and also carbon fibers. Their fiberlength or particle size is generally 5 to 3000 μm, preferably 10 to 1000μm, particularly preferably 15 to 500 μm.

Suitable inorganic fillers are, in particular, fibers or essentiallyspherical particles made of glass (for example glass fibers, glassfilaments, glass staple fibers), rockwool short fibers (for examplebasalt wool, slag wool or mineral wool fibers), carbonates (for examplechalk, limestone flour, calcite, precipitated calcium carbonate,magnesium carbonate, dolomite or barium carbonate), sulfates (forexample barium sulfate or calcium sulfate), silicates (for example talc,pyrophyllite, chlorite, hornblend, mica, kaolin, wollastonite, slateflour, precipitated Ca, Al, Ca/Al, Na/Al silicates, feldspars, mullite,zeolites, silica, quartz, fused quartz, cristobalite, kieselguhr,Neuburger silicon dioxide, precipitated silica, pyrogenic silica, glassflour, pumice flour, perlite, glass (micro)beads (whole glass beads),aluminosilicate hollow beads, Ca metasilicates), or oxides (for examplealuminum hydroxide, magnesium hydroxide, titanium dioxide). The fiberlength or particle size of the inorganic fillers is generally 0.1 to3000 μm, preferably 0.1 to 500 μm, particularly preferably 1 to 250 μm.

In a preferred embodiment, the inorganic filler consists of glassmicrobeads of a mean diameter of 1 to 250 μm, preferably 2 to 150 μm.These are preferably composed of 70 to 73% by weight of SiO₂, 13 to 15%by weight of Na₂O, 7 to 11% by weight of CaO, 3 to 5% by weight of MgO,0.5 to 2% by weight of Al₂O₃ and 0.20 to 0.60% by weight of K₂O. Thesurface of the glass microbeads is expediently modified with an adhesionpromoter which enhances the adhesion to surrounding polymers. It ispossible to use, for example, commercially available glass microbeadswhich are modified so that they adhere well to acetals, tostyrene/acrylonitrile copolymers, acrylonitrile/butadiene/styrene (ABS)copolymers, cellulose, polyesters (especially poly(butyleneterephthalate)), polyamides, polyolefins (especially polyethylenes),polycarbonates, poly(methylene(meth)acrylate)s, poly(phenylene oxide)s,polypropylenes, polystyrenes, polysulfones, or poly(vinyl chloride)s.

The roughness of the inventive food casing may be set via the contentand particle size of the fillers. It preferably has a maximum surfaceroughness R_(max), (determined in accordance with DIN 4768; E 1989) of 3to 60 μm, particularly preferably 6 to 45 μm, a mean roughness R_(a)(determined in accordance with DIN 4762; E 1989) of 0.5 to 10 μm,preferably 0.8 to 7 μm, particularly preferably 1.2 to 6.5 μm, and amean surface roughness R_(z) (determined in accordance with DIN 4768; E1989) of 1 to 45 μm, preferably 2 to 35 μm, particularly preferably 3 to32 μm.

A peculiarity of collagen casings is their high water-retentioncapacity. This effect, in the case of the inventive casing, may beimitated by fillers which are highly swellable and act likesuperabsorbents. In the case of scalded-emulsion sausages, thisdecreases the loss of juice in an outer package. Suitable substancesare, in particular, sulfate-, carboxylate- or phosphate-containingfillers, or those having quaternary ammonium groups. Likewise, nonionicfillers having high swelling capacity are suitable. The fillers can becrosslinked, uncrosslinked, branched or unbranched. Those which can beused are, for example, natural organic thickeners, such as agar agar,alginates, pectins, carrageenans, tragacanth, gum arabic, guar seedmeal, carob bean meal and gelatin, and in addition also modified organicnatural substances such as (sodium)carboxymethylcellulose, sodiumcarboxymethylethylcellulose, methylhydroxyethylcellulose,methylhydroxypropylcellulose, hydroxyethylcellulose and carboxymethylstarch. In addition, it is also possible to use inorganic thickeners(for example silica or polysilica), clay minerals, such asmontmorillonite or zeolites. Fully synthetic thickeners which can beused are vinyl polymers, polycarboxylic acids, polyethers, polyiminesand polyamides. In addition superabsorbents based on polyacrylate orpolymethacrylate can be used.

The total content of filler(s) is generally 1 to 50% by weight,preferably 2 to 40% by weight, particularly preferably 2 to 35% byweight, in each case based on the total weight of the thermoplasticmixture. At a high filler content, the casing may be torn like paper andcan be coiled off from the sausage-meat emulsion.

If appropriate, the thermoplastic mixture may also comprise othersynthetic polymers. These are in particular ionomers, polymerscontaining (meth)acrylic esters, or polymers containing vinyl esterunits. These polymers are partially incompatible with polyamides, sothat a grained inhomogeneous surface structure results. This isabsolutely desirable, since the inventive casing then looks more similarto a collagen skin or fiber skin. The casing also as a result becomessofter and less brittle. At a filler content of more than 5% by weight,the casing can otherwise be brittle in some cases.

The ionomer is generally a copolymer having a large content of units ofhydrophobic monomers and small amounts of comonomers containing ionicgroups. The ionic groups can be bound directly to the main chain of thecopolymer. They can also be bound to side chains thereof. Preferredionomers are ethylene/(meth)acrylic acid copolymers in which some of thecarboxyl groups can be present as sodium or zinc carboxylate groups.

The (meth)acrylic ester polymer is preferably an ethylene/methylacrylate, an ethylene/ethyl acrylate or an ethylene/butyl acrylatecopolymer. The vinyl ester polymer is for example a poly(vinyl acetate),an ethylene/vinyl acetate copolymer or a copolymer containing units ofvinyl acetate and 2-ethylhexyl acrylate, crotonic acid, vinyl chloride,vinyl laurate, dibutyl maleate, dioctyl maleate or maleic anhydride. Itcan also be a terpolymer containing units of vinyl acetate, butylacrylate and N-(2-hydroxyethyl)acrylamide, a terpolymer containing unitsof vinyl acetate, ethylene and vinyl chloride, or a terpolymercontaining units of vinyl acetate, ethylene and acrylamide. The vinylacetate copolymers also cover partially saponified poly(vinyl acetate)s,also termed poly(vinyl acetate-co-vinyl alcohols).

The content of ionomer, (meth)acrylic ester polymers and/or vinyl esterpolymers is generally 1 to 30% by weight, preferably 1.5 to 25% byweight, particularly preferably 2 to 17% by weight.

The addition of a plasticizer is advisable. This simplifies processingon blown-film plants, since the material is less brittle. Furthermore,the better digestion of the filler component gives a more homogeneousfilm structure, which is desired for certain applications.

Preferred plasticizers are dimethyl sulfoxide (DMSO), butane-1,3-diol,glycerol, water, ethylene glycol, butylene glycol, diglyceride, diglycolether, formamide, N-methylformamide, N,N-dimethylformamide (DMF),N,N-dimethylurea, N,N-dimethylacetamide, N-methylacetamide,poly(alkylene oxide), glycerol mono-, di- or triacetate, sorbitol,erythritol, mannitol, gluconic acid, galacturonic acid, glucaric acid,glucuronic acid, polyhydroxycarboxylic acids, glucose, fructose,sucrose, citric acid or citric acid derivatives, or poly(vinyl alcohol).Type and amount of plasticizer(s) depend on the fillers chosen in eachcase and may be optimized by simple preliminary experiments.

The content of plasticizer is up to 30% by weight, preferably 1 to 25%by weight, particularly preferably 2 to 20% by weight, in each casebased on the total weight of the thermoplastic mixture.

If desired, the inventive casing can be colored by dyes and/or pigments.On stretching, cavities (vacuoles) can form around the pigmentparticles. The vacuoles additionally increase the smoke permeability ofthe film. The dyes or pigments are expediently added to thethermoplastic mixture before extrusion. In addition, if required,additives can be added which affect the sausage-meat emulsion adhesion.In principle, those which are suitable are nitrogenous compounds andcarboxyl-group-containing compounds. Improved sausage-meat emulsionadhesion can also be achieved by physical processes such as coronatreatment.

The inventive casing can also be multilayered. It then generallycomprises 2 to 5 layers. The further layers are, for example, thosebased on polyolefins and/or polyamides. The filler-containing layer,which gives the casing the desired rough surface structure, forms inthis case the outer layer. Between the individual layers, in addition,thin (about 1 to 5 μm thick) layers can also be situated, which containadhesion promoters. Suitable adhesion promoters are, in particular,polyolefins which are modified with functional groups (for example bygrafting with maleic anhydride). Adhesion promoters can equally wellalso be a constituent of the layers based on polyolefins or polyamides.In a preferred embodiment, at least one adhesion promoter isincorporated into the polyolefin layer. The total thickness of themultilayer casing is generally in the same range as the total thicknessof the single-layer casing.

The inventive casing is particularly suitable for hot smoking (above 50C), and under certain conditions also for warm smoking (25 to 50 C).However, it is less suitable for cold smoking (up to 25 C). Theintensity of the smoke aroma and smoke color transferred to the food(this is in particular sausage-meat emulsion) increases with increasingtemperature of the smoking gas. Furthermore, the smoke, owing to itsaldehydic, phenolic and acid-containing constituents, also has apreservative, antioxidant and solidifying action.

The inventive casing may be produced free of hygienic defects in uniformquality. The production process is considerably simpler than thecollagen process. Finally, the casing can be processed for end use usingknown processes (printing, ring-forming, shirring).

The inventive food casing is produced generally by a blown-tube processor by biaxial stretch orientation. In the case of the blown-tubeprocess, the extruded flexible tube is stretched in the peripheraldirection (transverse direction) by inflation and in the longitudinaldirection by take-off rolls. Since the shaping takes place immediatelyfrom the melt, the degree of orientation of the polymer chains is low.In the case of biaxial stretch orientation, a flexible tube ofrelatively high wall thickness is first produced by extrusion. This tubeis inflated only a little or not at all. Then what is termed the primarytube is cooled. Not until a later step is the primary tube heated to thetemperature necessary for the biaxial stretch orientation and thenbiaxially stretch-orientated by an internally-acting gas pressure and bytake-off rolls. By this means a high degree of orientation of thepolymer chains is achieved, much higher than in the case of a blownfilm.

The inventive seamless tubular casing preferably has a thickness of from40 to 200 μm, when it is made by a blown-tube process, and a thicknessof from 25 to 75 μm, when it was obtained by biaxial stretch orientation(double bubble process). Seamless tubular casings which are to be usedas artificial sausage casings are preferably produced by biaxial stretchorientation. After the biaxial stretch orientation, expediently therefurther follows a partial or complete thermosetting. By means of thethermosetting, the casing shrinkage can be set to the desired value.Artificial sausage casings generally have a shrinkage of less than 20%in the longitudinal and transverse directions if they are laid for 1 minin water at 90 C.

The tubular casing can then be further finally processed to givesections tied off at one end. It can also be shirred in sections to giveshirred sticks. In addition, it can be bent to form a ring casing. Forthis the casing is exposed on one side to heat radiation or hot air.Special natural gut skin shapes are also possible, for example the fatend.

Processes and apparatuses for making ring shapes from polymer casingsare familiar to those skilled in the art.

The examples hereinafter were produced according to the process 1 or 2described below and illustrate the invention. Percentages arepercentages by weight unless stated otherwise or it is obvious from thecontext. The components specified in the examples were in each casemixed in a twin-screw extruder and thermally plasticized.

Process 1:

The organic filler was first charged into the extruder and a plasticizerwas added. The temperature in the extruder was increased over aplurality of zones from about 90 to about 180 C. The (co)polyamide orthe mixture of (co)polyamide and polyether block amide and, ifappropriate, further additives were then fed into the extruder and mixedwith the remaining constituents at temperatures between 200 and 230 C(depending on the melting point of the polyamide) and the thermoplasticmelt formed therefrom was extruded. The extrudate was finally comminutedto form granules.

Process 2:

In this case first the (co)polyamide or the mixture of (co)polyamide andpolyether block amide and, if appropriate, further additives was/werefed into the extruder and mixed at temperatures between 200 and 300 C(depending on the melting point of the polyamide). Thereafter, theorganic or inorganic filler was added. A plasticizer is not absolutelyrequired in this case. The thermoplastic mixture was finally comminutedto form granules.

The granules were then processed to form a tubular film by afilm-blowing process or by biaxial stretch orientation. Multilayercasings were produced by coextrusion using a multilayer die, thefiller-containing layer forming the outer layer.

In the examples the following were used:

-   -   ethylene/methacrylic acid copolymer, partially neutralized with        zinc ions (®Surlyn 9020 and ®Surlyn 1650 from DuPont)    -   ethylene/methyl acrylate copolymer (containing 24% methyl        acrylate) (®Elvaloy 1224AC from DuPont)    -   ethylene/acrylic acid copolymer (as free acid) (®Nucrel 31001        from DuPont)    -   nylon 6/poly(ethylene glycol) block copolymer (®Pebax MH 1657 SA        from Elf Atochem S.A.)    -   nylon 12/poly(ethylene glycol) block copolymer (®Pebax MV 1074        SA from Elf Atochem S.A.)    -   nylon 6/6.6 (®Ultramid C4 from BASF Aktiengesellschaft)    -   nylon 6 (®Grilon F40 from Ems Chemie AG)    -   nylon 6.6 (®Ultramid A5 from BASF Aktiengesellschaft)    -   nylon 12 (®Grilamid L25 from Ems Chemie AG)

Composition and properties of the tubular casings according to examples1 to 14 are compiled in tables 2 and 3. TABLE 1 1 4 Thermoplastic 2 3Further mixture Filler Plasticizer additives a (co)polyamidepolysaccharide or plasticizer ionomers for stability inorganic fillerand/or and sausage- (meth)acrylic meat emulsion ester polymers adhesionand/or vinyl ester polymers b blend of natural feel suppleness natural(co)polyamide and properties/optical graininess glycol- or propertiespolyglycol- coiling ability digestion inhomogeneous modified water-vaporof the surface polyamide and smoke natural structure for stability,permeability material reduction of sausage-meat control of brittlenessemulsion the water- adhesion, retention water-vapor capacity andimproved smoke permeabilityThe following raw Material combinations are conceivable:[1](a)+[2] //[1](b)+[2] //[1](a)+[2]+[3] //[1](b)+[2]+[3](a)+[2]+[4]//[1](b)+[2]+[4] //[1]l ( a)+[2]+[3]+[4] //[1](b)+2]+[3]+[4]

TABLE 2 Example Thermoplastic component Filler Plasticizer Process 1  4%by wt. Quartz flour 87.0% by wt. Ultramid A5  9% by wt. Glass microbeads— — 2 2 97.0% by wt. Ultramid A5  3% by wt. Calcium carbonate — — 2 358.5% by wt. Ultramid C4  4% by wt. Cellulose powder 18.0% by wt. GrilonCF6S 6% by wt. Glycerol 1 13.5% by wt. Pebax MH 1657 4 96.0% by wt.Ultramid C4  4% by wt. Cellulose powder — — 2 5 62.5% by wt. Ultramid C4 4% by wt. Cellulose powder — — 19.0% by wt. Grilon CF6S 2 14.5% by wt.Pebax MH 1657 6 70.0% by wt. Grilamid L25  5% by wt. Guar seed meal — —2 25.0% by wt. Pebax MV 1074 7 80.0% by wt. Grilon F40 10% by wt. Maizestarch 3% by wt. Glycerol 1  7.0% by wt. Pebax MH 1657 8   61% by wt.Ultramid A5  9% by wt. Glass microbeads   15% by wt. Nucrel 31001  4% bywt. Quartz flour — — 2   11% by wt. Grilon F 40 9   71% by wt. UltramidA5  9% by wt. Glass microbeads   5% by wt. Elvaloy AC 1224  4% by wt.Quartz flour — — 2   11% by wt. Grilon F 40 10   71% by wt. Ultramid A5 9% by wt. Glass microbeads   5% by wt. Surlyn 9020  4% by wt. Quartzflour — — 2   11% by wt. Grilon F 40 11   66% by wt. Ultramid A5  9% bywt. Glass microbeads   10% by wt. Surlyn 9020  4% by wt. Quartz flour —— 2   11% by wt. Grilon F 40 12   67% by wt. Ultramid C4  4% by wt.Cellulose powder   10% by wt. Nucrel 31001 4% by wt. Glycerol 1   15% bywt. Pebax MH 1657 13   72% by wt. Ultramid C4  4% by wt. Cellulosepowder   10% by wt. Surlyn 1650 4% by wt. Glycerol 1   10% by wt. PebaxMH 1657 14   69% by wt. Ultramid C4   5% by wt. Surlyn 1650 10% by wt.Maize starch 6% by wt. Glycerol 1   10% by wt. Pebax MH 1657

TABLE 3 σ₁₅ value)² Tear strength)2 Elongation at longitudinal/longitudinal/ break)2 Roughness Film Example WVP)¹ transverse transverselongitudinal/transverse Ra/Rz/Rmax Glossiness thickness No. [g/m2d][N/mm2] [N/mm2] [%] [μm] 20°/60°/85° [μm] 1 10 19/19 24/23 85/712/8.4/16.9 6.3/29.1/22.2 89 2 8 41/30 37/30 109/99  1.2/5.9/8.37.4/39.4/26.1 90 3 49 16/15 54/53 451/489 2.0/10.5/14 0.5/6.0/4.2 80 440 20/18 60/52 490/460 1.9/10.1/13 0.6/6.1/4.5 70 5 48 16/15 54/49434/440 2.1/11/15 0.5/6.3/4.3 64 6 16 18/17 50/49 401/395 1.8/9.7/12.50.7/7.0/5.2 75 7 30 20/19 52/50 397/396 0.7/3.0/4.8 4.5/23.1/16.2 52 811 16/16 25/20 150/100 2.9/14.8/23.9 5.8/25.1/19.2 90 9 11 19/17 26/23140/90  1.9/10.7/13.4 6.4/30.0/22.1 90 10 11 16/15 25/22 120/80 2.1/12.3/19.8 6.5/27.0/20.2 90 11 10 18/17 26/20 120/60  2.2/9.3/14.06.0/25.9/20.1 96 12 38 15/14 50/48 425/410 2.0/9.8/12.7 0.6/6.5/4.4 7013 30 16/16 52/49 401/392 1.8/9.7/12.5 0.5/6.2/4.1 70 14 48 19/19 49/47380/370 0.8/3.1/5.0 4.2/22.1/15.4 60)¹WVP = water vapor permeability. The casing was charged at one end withair of a relative humidity of 85% at 23 C.; the water vapor permeabilitywas determined as specified in DIN 53 122.)²Examples 1, 2 and 8 to 11 were determined as specified in DIN 53 455on wet samples of width 15 mm at a clamped length of 50 mm, examples 3to 7 and 12 to 14 on dry samples.

COMPARATIVE EXAMPLE 1 (WO 99/61524)

As described in the examples above, a tubular film was produced from athermoplastic mixture of the type specified in WO 99/61524. The mixturespecifically contained the following: 42% by weight of thermoplasticpolyesterurethane 35% by weight of corn starch 23% by weight of glycerol

The finished film had a thickness of 120 μm. Its σ₁₅ value was 4.2 N/mm²and its water vapor permeability was 200 g/m²d. The roughness parametersR_(a)/R_(z)/R_(max) were 0.3/1.8/2.4 μm.

Despite a higher thickness, this film had a lower mechanical stability(recognizable from the sigma-15 value) than that of the inventive film.In addition, the roughness of the casing was markedly less.

COMPARATIVE EXAMPLE 2 (EP-A 935 423)

As described above, a tubular film was produced from a thermoplasticmixture of the following composition: 38% by weight of Grilon F40 27% byweight of Ultramid C4 35% by weight of Grilon FE 7012

The finished film had a thickness of 25 μm and a water vaporpermeability of 75 g/m²d. The roughness parameters R_(a)/R_(z)/R_(max)were 0.5/3.0/3.7 and the glossiness at 20/60/85 was 13.5/82.1/87.6.

The inventive film, in contrast, had a markedly lower water vaporpermeability, a glossiness lower by some orders of magnitude and a morenatural roughness.

1. A single-layer or multilayer food casing made of a thermoplasticmixture having at least one aliphatic polyamide and/or copolyamide,wherein the mixture comprises at least one inorganic and/or organicfiller, the casing having a maximum surface roughness R_(max),determined in accordance with DIN 4768, of 3 to 60 μm, and a water vaporpermeability at a mean thickness of 100 μm, determined as specified inDIN 53122, of less than 50 g/m²d.
 2. The food casing as claimed in claim1, wherein it has a water vapor permeability, determined as specified inDIN 53122, of 1 to 49 g/m²d.
 3. The food casing as claimed in claim 1,wherein the (co)polyamide is nylon 4.6, nylon 6, nylon 6.6, nylon 6/6.6,nylon 6.9, nylon 6.10, nylon 6.12, nylon 6/66.9, nylon 6/66.12 or nylon12.
 4. The food casing as claimed in claim 1, wherein the thermoplasticmixture additionally comprises at least one aliphatic and/or partlyaromatic copolyamide having glycol units and/or polyglycol units.
 5. Thefood casing as claimed in claim 4, wherein the aliphatic and/or partlyaromatic copolyamide having glycol and/or polyglycol units has a) atleast one amide part having units a1) of at least bifunctional aliphaticand/or cycloaliphatic amines and of at least bifunctional aliphaticand/or cycloaliphatic and/or aromatic carboxylic acids, or a2) ofaliphatic aminocarboxylic acids or lactams thereof or a3) mixtures ofa1) and a2) and b) at least one glycol or polyglycol part containingunits b1) of an at least bifunctional aliphatic and/or cycloaliphaticalcohol having from 2 to 15 carbon atoms, in particular from 2 to 6carbon atoms, or b2) of at least one oligoglycol or polyglycol of one ofthe alcohols specified in b1) or b3) of at least one aliphaticoligoglycol or polyglycol of the type specified in b2), the terminalhydroxyl groups of which are replaced by amino groups or b4) of amixture of b1), b2) and/or b3) or b5) of an ester-containing polyglycolpart formed from at least bifunctional aliphatic alcohols and at leastdivalent aliphatic, cycloaliphatic and/or aromatic dicarboxylic acids orb6) of a mixture of b1), b2) and/or b5).
 6. The food casing as claimedin claim 1, wherein the amount of (co)polyamide is 50 to 99% by weight,and the total amount of inorganic and/or organic filler is 1 to 50% byweight, in each case based on the total weight of the thermoplasticmixture.
 7. The food casing as claimed in claim 4, wherein the amount of(co)polyamide is 35 to 98% by weight, the amount of polyether blockamide is 1 to 35% by weight, and the amount of filler is 1 to 50% byweight, in each case based on the total weight of the thermoplasticmixture.
 8. The food casing as claimed in claim 1, wherein the organicfiller is a carbohydrate.
 9. The food casing as claimed in claim 1,wherein the filler is highly swellable.
 10. The food casing as claimedin claim 1, wherein the inorganic filler comprises fibers and/orspheres.
 11. The food casing as claimed in claim 10, wherein the fiberlength or particle size of the inorganic filler is 0.1 to 3000 μm. 12.The food casing as claimed in claim 10, wherein the fibers and/orspheres comprise glass microbeads having a mean particle size of 1 to250 μm.
 13. The food casing as claimed in claim 12, wherein the surfaceof the glass microbeads is modified with an adhesion promoter whichenhances the adhesion to surrounding polymers.
 14. The food casing asclaimed in claim 1, wherein the thermoplastic mixture additionallycomprises at least one ionomer, a (meth)acrylic ester polymer and/or avinyl ester polymer.
 15. The food casing as claimed in claim 14, whereinthe ionomer is an ethylene/(meth)acrylic acid copolymer in which some ofthe carboxyl groups are if appropriate present as zinc or sodiumcarboxylate groups.
 16. The food casing as claimed in claim 14, whereinthe (meth)acrylic ester copolymer is an ethylene/methyl acrylate,ethylene/ethyl acrylate and/or an ethylene/butyl acrylate copolymer. 17.The food casing as claimed in claim 14, wherein the vinyl ester polymeris a poly(vinyl acetate), an ethylene/vinyl acetate copolymer, acopolymer containing units of vinyl acetate and 2-ethylhexyl acrylate,crotonic acid, vinyl chloride, vinyl laurate, dibutyl maleate, dioctylmaleate or maleic anhydride, a terpolymer containing units of vinylacetate, butyl acrylate and N-(2-hydroxyethyl)acrylamide, a terpolymercontaining units of vinyl acetate, ethylene and vinyl chloride, or aterpolymer containing units of vinyl acetate, ethylene and acrylamide.18. The food casing as claimed in claim 14, wherein the content ofionomer, (meth)acrylic ester polymer and/or vinyl ester polymer is 1 to30% by weight, based on the total weight of the thermoplastic mixture.19. The food casing as claimed in claim 1, additionally comprising aplasticizer, the content of plasticizer being up to 30% by weight, basedon the total weight of the thermoplastic mixture.
 20. A process forproducing a food casing as claimed in claim 1, which comprises extrudingor coextruding the thermoplastic mixture having at least one aliphaticpolyamide and/or copolyamide and at least one inorganic and/or organicfiller and blow-forming or biaxially stretch-orienting the resultantflexible tube.
 21. The process as claimed in claim 20, wherein theflexible tube is finally processed to give sections tied off at one endor to give a shirred stick.
 22. The process as claimed in claim 20,wherein the flexible tube is further processed to give a naturalgut-skin-like shape.
 23. An artificial sausage casing, preferably forscalded-emulsion sausage comprising a food casing as claimed in claim 1.24. A single-layer or multilayer food casing made of a thermoplasticmixture having at least one aliphatic polyamide and/or copolyamide,wherein the mixture comprises at least one inorganic and/or organicfiller, the casing having a maximum surface roughness R_(max),determined in accordance with DIN 4768, of 6 to 60 μm, a mean roughnessR_(a) determined in accordance with DIN 4762, of 1.2 to 10 μm, and awater vapor permeability at a mean thickness of 100 μm, determined asspecified in DIN 53122, of less than 50 g/m²d.
 25. A food casing ofclaim 9 wherein said fibers and/or spheres are selected from the groupconsisting of glass filaments, glass staple fibers, glass microbeads,mineral wool fibers, short mineral wool fibers, carbon fibers, zeolites,quartz, aluminosilicate hollow beads, silicon dioxide, silicic acids,sulfates, preferably barium sulfate or calcium sulfate, carbonates,preferably calcium carbonate and magnesium carbonate, aluminumhydroxide, oxides, preferably titanium dioxide, talc, clay and mica. 26.A food casing of claim 12 wherein said glass microbeads comprise onaverage of 70 to 73% by weight of SiO₂, 13 to 15% by weight of Na₂O, 7to 11% by weight of CaO, 3 to 5% by weight of MgO, 0.5 to 2.0% by weightof Al₂O₃ and 0.20 to 0.60 of K₂O.